1. Field of the Invention
The present invention relates to a metal oxide thin film substrate, a method of fabricating the same and a photovoltaic cell and organic light-emitting device (OLED) including the same, and more particularly, to a metal oxide thin film substrate which can increase light trapping efficiency and light extraction efficiency, a method of fabricating the same and a photovoltaic cell and OLED including the same.
2. Description of Related Art
In general, the use of a transparent metal oxide thin film is determined depending on its conductivity. For example, the transparent metal oxide thin film can be used for a transparent conductive oxide electrode of a photovoltaic cell or a light extraction layer which is intended to increase light extraction efficiency of an organic light-emitting device (OLED).
Zinc oxide (ZnO) is a typical substance used for the metal oxide thin film which forms a transparent conductive oxide electrode of a photovoltaic cell and a light extraction layer of an OLED. Here, ZnO is formed as a thin film which coats a glass substrate by, for example, sputtering or atmospheric pressure chemical vapor deposition (APCVD) that is regarded as being suitable for mass production due to its rapid coating rate and high productivity, thereby forming a transparent electrode for a photovoltaic cell or a light extraction layer of an organic light-emitting device.
The metal oxide thin film has superior light efficiency as the haze value thereof increases. The haze value is determined by the texture formed on the surface of the metal oxide. When the metal oxide thin film is used for a transparent conductive oxide electrode of a photovoltaic cell, doping by adding an external element is required in order to increase electrical conductivity. However, doping smoothens the surface shape of the texture, thereby lowering the haze characteristic of the metal oxide thin film. In contrast, when the haze value of the metal oxide thin film is increased by controlling the texture shape of the surface of the metal oxide thin film in order to improve light efficiency, the sheet resistance Ω/□ of the metal oxide thin film increases, thereby deteriorating the electrical characteristics of the metal oxide thin film, which is problematic.
In addition, when the metal oxide thin film is used for a light extraction layer, a high haze value is required. In order to increase the scattering characteristic using only the texture on the surface, a texture thickness of at least 3 μm is required. In this case, however, light absorption is increased, that is, light transmission is decreased, thereby reducing light extraction efficiency, which is problematic.
Accordingly, the related-art methods of controlling the surface structure have limited ability to improve the scattering characteristic.
The information disclosed in the Background of the Invention section is provided only for better understanding of the background of the invention, and should not be taken as an acknowledgment or any form of suggestion that this information forms a prior art that would already be known to a person skilled in the art.